Process of smelting iron ores



(NoModeL) N. A. PRATT.

PROCESS OF SMELTING IRON 033's.

No. 413,552. Patented Oct. 22, 1889:

N. PETERS, Plum-mm n or. Wuhinglon. D. c.

UNITED STATES PATENT OFFICE,

NATHANIEL A. PRATT, OF ATLANTA, GEORGIA, ASSIGNOR TO THE PRATT STEELCOMPANY, OF BIRMINGHAM, ALABAMA.

PROCESS OF SMELTING IRON ORES.

SPECIFICATION forming part of Letters Patent No. 413,552, dated October22, 1889. Application filed June 2, 1888. Serial No. 275,943. (Nospecimens.)

T0 ctZZ whom it may concern.-

Be it known that I, NATHANIEL A. PRATT, a citizen of the United States,residing at Atlanta, in the county of Fulton and State of Georgia, haveinvented certain new and useful Improvements in the Process of SmeltingIron Ores andI do hereby declare the following to be a full, clear, andexact description of the invention, such as will enable others skilledin the art to which it appertains to make and use the same.

My invention relates to processes of smelting ores for dephosphorizingand otherwise refining metals; and it consists in the improved processof smelting the ore and dephosphorizing the metal by a single treat mentin the blastfurnace, as hereinafter fully disclosed in the descriptionand claims in connection with the drawing.

The objects of my invention are, first, to smelt ore and dephosphorizeand otherwise purify and refine metal by a single treatment in theblast-furnace; second, to introduce finely-comminuted basic flux intothe smelting-furnace at or near the zone of fusion; third, to shield andprotect the ore and molten metal from contact with silica or otheracids; fourth, to smelt the ore at the lowest temperature possiblecompatible with fusion; fifth, to obtain the molten metal in as. smallparticles, bodies, or globules as possible, and, sixth, to introduceoxygen into direct contact with said small particles or globules of themolten metal. I accomplish these objects in connection with theapparatus shown'in the accompanying drawings, forming part of thisspecification, in which the same reference-numerals indicate the sameparts, and in which the figure repre-. sents a vertical section of aconstruction of apparatus which may be employed for carrying out myprocess, showing the furnace and one of the flux feeders or injectorsand their belongings.

In the drawing, the numeral 1 indicates the furnace, the boshes 2 andcrucible 3 of whichare provided with a lining 4 of any suitable basiccompound which does not contain any silica or silicious compound orother acid The bustle or blast-pipe 5 surrounds said fur nace, and isprovided with the usual droppipcs 6, having the blast-nozzles 7, whichenter said furnace through the tuyeres 8 at the lower part of theboshes. A number of fluxinjectors (only one of which is shown) forinjecting pulverized basic flux into the furnace are arranged aroundsaid furnace and provided with hoppers 9, having dischargepipes 10extended through the walls of the furnace, preferably at a shortdistance above the tuyeres; but like result may be effected by arrangingthem at or within said tuyeres. These flux injectors or feeders may beof any suit-able construct-ion, since all that is required of them isthat they shall be capable of injecting finely-comminuted flux againstthe outward pressure of the blast in the furnace, either through specialflux-nozzles or through the air-main and blast-nozzles. However, for thepurpose of giving an example of a feeder or injector that is capable ofuse in practicing my process, I herein illustrate and describe anapparatus which forms the subject of an application for Letters Patentfiled by me simultaneously herewith, Serial No. 275,942. In thisapparatus the hoppers 9 are formed at their lower ends withinwardly-converging sides 10 and supported a short distance outside ofthe furnace, and are preferably arranged at equal distances around thesame. Each of these hoppers is provided with a dischargepipe 10, theinner end 11 of which is formed in the shape of a funnel or hollow cone12 and se cured within said hopper, and its outer end is provided with aslidable coupling or tube section 13, which registers with and isadapted to enter with its outer tapering end into a flux-nozzle 14. Thisflux-nozzle passes through the wall of the furnace, preferably in thelower part of the boshes and a short distance above the tuyeres andblast-nozzle; but it may be arranged below the latter. A suitable stopcock or valve 15 is placed in the discharge-pipe 10 between the slidingcoupling 13 and the hopper 9. A compressed-air or injector pipe 16slides in a stoning-box 17 in the side of the hopper, diametricallyopposite the funnel-shaped inner end of the discharge-pipe, and isprovided with a conical too This injector-pipe 16 is also providedoutside ceiver 24, whichis fed from a suitable airof the stuffing-box 17with a rack 19, which is engaged by a cog-wheel or pinion 20, which isprovided with a suitable handle 21, or similar means for revolving it. Astop cock 0r valve 22 is also provided in said injectorpipe 16 outsideof said rack; also, the outer end of this pipe is adapted to slide inthe packed end of a blast-conveying pipe 23, which extends from acompressed-air recompressor or blowing-engine; or said pipe may be feddirectly from the air-compressor or blowing-engine.

The operation of this form of flux feederor injector is as follows:After the hopper of the apparatus has been charged withfinely-comminuted flux, and when the compressed-air reservoir has alsobeen charged or the compressor or blowing-engine started, and when thefurnace has been started in operation, the sliding coupling is drawn outto. enter the flux-nozzle. Then the injector-pipe 16 is slid back by thepinion and rack, so as to open the funnel-shaped end 12 of thedischarge-pipe 10. Then the stop-cock 15 in said discharge-pipe isopened, and then the stop-cock 22 in the injector pipe is also opened.The blast of compressed air in the injector-pipe will then draw thefinely-com.- minuted flux into the funnel-shaped end of thedischarge-pipe and blow it through said pipe, the sliding coupling, thenozzle, and into the body of the furnace. The feed of the apparatus maybe stopped by slidingthe injector-pipe into its seat .in thefunnelshaped end of the discharge-pipe, when the stop-cocks may beclosed and the coupling 13 slid back from the flux-nozzle. The supply offlux forced into the furnace and the quantity of the same in proportionto the strength of the forcing-blast may be regulated by adjusting theinjector-pipe toward or from the funnel-shaped end of thedischarge-pipe. For instance, by drawing said injector-pipe away fromsaid funnel-shaped end a greater supply of flux will be fed into thefurnace, but with comparatively less airforce, and by'pushin g saidinjector-pipe farther toward said funnel-shaped end a less supply offlux will be fed, but with comparatively greater air-force. The force ofthe blast may also be regulated by the stop-cocks upon the discharge andinjector pipes.

In the present process, which may be carried out in the above-describedapparatus, when the furnace is charged with ore and fuel in the usualmanner, the furnace set in operation, and the blast started, care mustbe taken that the metal which drops or trickles down in small globulesor bodies from the ore shall not come in contact with any silicious orother acid, excepting what may be naturally present in the fuel or ore.As the globules or small particles of molten metal drop down through theboshes and into the crucible of the furnace they are acted upon by theblast which supplies the necessary oxygen thereto, and by thefinely-comminuted flux, which comes into intimate contact with eachparticle thereof, and thus the molten metal by the com bined actionthereon of said blast and comminuted flux will be completely dephosphorized, desiliconized, and otherwise purified and refined and deliveredinto the crucible in a perfect state, as the basic finely-comminutedflux will have had the desired effect upon it by having been introducedunder the most favorable circumstances at or near the zone of fusion.Care must be taken in operating the furnace that as low heat ismaintained within the same as is consistent with reducing the metal inthe ore to a fluid state, since high heat tends to increase theabsorption of silicon, and, as experience shows, renders the eliminationof phosphorus far more difficult. However, to effect a proper operationof the furnace to this end it is not possible to specify the necessaryor exact pressure of blast, or

to state given pyrometric tests of the neces sary temperature therein,as it is well known that these conditions must be varied in accor-dancewiththe character of the different kinds of ores undergoing treatmentand of the fuels and fluxes employed. There are no predeterminedcharacteristics or conditions of ore, fuel, and flux, as they vary indifferent localities, and consequently the degrees of heat forproperlyreducing the metals have to be varied accordingly. Therefore asthe character or structure of the ores will often differ the required ornecessary amount of heat in the furnace must be left to the experienceandjudgment of the attendant, Who must in all instances observe that notenough heat is applied to effect the absorption of foreign matters bythe molten metal or to prevent proper elimination of phosphorustherefrom.

The novelty or distinguishing characteristics of my process will bestappear from a detailed explanation of the working thereof. The furnace,being blown in, is supplied with the usual charge of fuel and ore, alllimestone flux being omitted, and in its place is added an equal weightof additional. ore. As combustion goes on below, this mass of ore andfuel descends slowly through zones of increasing heat and practicallymaintains its original bulk and proportions. The ore, essentially aferric oxide, parts with its oxygen and is slowly reduced to a loweroxide and ultimately to porous or spongy metal, and at the same time thecarbon of the fuel and of the ascending gases impregnates the mass ofspongy metal and carbonizes the same. other reactions take place in theupper boshes and stack. The impurities of the ore-:viz, clay, sand,&c.sink with the ore and fuel, practically unchanged, down into theboshes,

where the heat becomes sufficient, to fuse or soften the carbonizedspongy iron. The clay, sand, and other impurities, being more infusi blethan the spongy iron, remain practically unchanged. At this point,however, the finelycomminuted flux that has been injected and difiusedbelow rises in a fine dust with the ascending gases, is brought intointimate contact and chemical union with the silica, alumina, and othergross impurities of the ore and forms a fusible slag or cinder, whichtrickles down with the fused metal toward the hearth and crucible. Inthus descending to the lower boshes and zone of fusion and greatest heatthe fine deposited carbon that coats and impregnates the spongy iron andall solid matter in the furnace reacts on the impurities of the ore andfuel, reducing sand, clay, phosphates, sulphates, titanates, &c.,respectively, to silicon, aluminium, phosphorus, sulphur, titanium, &c.,all of which unite readily with the molten metal and form impure alloys,and in this condition descend to the fusion and oxidation zone ofgreatest heat just above the plane of the tuyeres and blast-nozzles.

Under existing methods the slags and fluxes have so far deteriorated inquality as to be incapable of active basic reaction on the oxidizedimpurities of the metal, the siliciousacid linings of thefurnaces addingto the difficulty and perhaps yielding their own silicon to the metal,the iron itself being thus frequently oxidized orburned for want ofproper protection by a fusible flux and falls to the crucible hearth asthe impure unrefined pigiron of the trade. On the other hand, with myprocess, as the impure molten metal in its descent enters theoxidizing-zone and passes in little streamlets or showers of globules ordrops it is immersed in the oxidizing atmosphere of the blast, in whichfloats and is ever present the active basic flux, which, in the absenceof an acid lining and its surroundings, unites instantaneously with theoxidized impurit-iessilicic, sulphuric, phosphoric, and titanic acidsandfloats them away in the slag. In the conduct of my process, if desired,a basic oxidizing flux may be diffused, thus increasing the intensity ofthe action in the oxidizing zone, whereby the percentage of carbon inthe metal may be reduced, resulting in the production of grade steel.

It is a well-known fact that the temperature at which a blast-furnace isoperated should be the lowest used in the processes of making iron andsteel, and this low temperature is the greatest safeguard againstexcessive reduction of silicon, titanium, manganese, and otherimpurities, and at same time it is the greatest promoter of theoxidation and removal of phosphorus and sulphur. Under this treatment ofore by my process the metal is drawn from the furnace in a purified anddephosphorized state, the refining having been accomplished in oneoperation in one and the same furnace. My processthus does away with thenecessity of subsequent purifying or refining the metal in anopen-hearth furnace, refiner, or converter; also, a greater output ofmetal is effected in the same space of time by my process than 'by thosecom-. monly employed, inasmuch as in my process cesses, as the flux,ore, and fuel graduallydescend into the zones of increasing heat, theflux has very little efiect upon theores, and,

while occupying undue space, will simply be calcined, whereas under myprocess this space is occupied by an equal bulk of ore;

also, when the flux employed in former processes arrives'at the zone offusion. where it is required to exert the basic reaction as essential tothe removal of the phosphorus from the metal, its basic quality andactivity. are so far neutralized and expended that it fails to effectsuch removal of the phosphorus and I its union with the impurities as isrequired for properly refining the metal,whereas this result is fullyeffected in my process by the finely-comminuted fiux, which acts,together with the oxygen of the blast, directly upon the globules orsmall bodies of metal while in its fresh and undiminished state ofactivity and strength; also, as the ore is protected from contact withall silicious and aluminous,

matters in my process, it will not be affected too thereby, excepting-bysuch as may be present" in the ore and fuel, and for this reason, thethe basic lining of the boshes and crucibleof the furnace performs animportant part in my-process. In this manner all the conditionsnecessary for dephosphorizing the metal-viz, first, a state of moltenmetal which will present a large oxidizable surface; second, the oxygensupplied by the blast in the shape of atmospheric air, or in other suitaable shape; third, the presence of an active basic oxide, supplied bythe pulverized flux, and, fourth, the lowest possible degree of heatconsistent with securing proper fluidity of themetal are all providedfor in the smelt ing-furnace by my process, so that What has hithertobeen accomplished by two separate processes-the smelting of the ore inthe blast-furnace and the dephosphorizing and refining or purifying ofthe metal thus produced in an open-hearth furnace, refiner, or

converter-is accomplished by me in one process and in one furnace.

Having thus fully described the various steps of my improved process andits subdivisions and the advantages thereof, what- I claim as new is 1.The improved process of smelting ores and dephosphorizing and otherwisepurifying and refining metal in a single blast-furnace, which consistsin smelting the ore in the presence of a basic lining, in shielding theore and molten metal from contact with silicious or other acids, and inintroducing finelycomminuted basic flux at or near the zone of fusionand into direct contact with the globules or small bodies of moltenmetal while being smelted, substantially asdescribed.

2. The improved process of smelting ores and dephosphorizing andotherwise purifying and refining metal in a single blastfurnace, whichconsists in smelting the ore in the presence of a basic lining, inshielding the ore and molten metal from contact with silicious or otheracids, and in introducing finelycomminuted basic flux at or near thezone of fusion and into direct contact with the globules or small bodiesof molten metal while being smelted, substantially as described.

3. The improved process of smelting ores and dephosphorizing andotherwise purifying and refining metal in a single blast-furnace, whichconsists in smelting the ore in the presence of a basic lining and atthe lowest temperature compatible with fusion, and in introducingfinely-comminuted basic flux at or near the zone of fusion and intodirect contact with the globules or small bodies of metal while beingsmelted, substantially as described.

4:. The improved process of smelting ores and dephosphorizing andotherwise purifying and refining metal in a single blast-furnace, whichconsists in smelting the ore in the presence of a basic lining and atthe lowest temperature compatible with fusion, in shielding or guardingthe ore and metal from contact with silicious or other acids, and inintroducing finely-comminuted basic flux at or near the zone of fusionand into direct contact with the globules or small bodies of moltenmetal while being smelted, substantially as described.

5. The improved process of smelting ores and dephosphorizing andotherwise purifying and refining metal in a single blast-furnace, whichconsists in smelting the ore in the presence of a basic lining and inintroducing the blast atthe zone of fusion, and in introducingfinely-comminuted basic flux at or near the zone of fusion above saidblast and into direct contact with the globules or small bodies ofmolten metal while being smelted, substantially as described.

6. The improved process of smelting ores and dephosphorizing andotherwise purifying and refining metal in a single blastfurnace, whichconsists in smelting the ore in the presence of a basic lining, inshielding or guarding the ore and metal from silicious and other acids,in introducing the oxidizing-blast at the zone of fusion, and inintroducing finely-comminuted basic flux at or near the zone of fusionabove said blast and into direct contact with the globules or smallbodies of molten metal while being smelted, substantially as described.

7. The improved process of smelting ores and dephosphorizing andotherwise purifying and refining metal in a single blast-furnace, whichconsists in smelting the ore in the presence of a'basic lining and atthe lowest temperature compatible with fusion, in omitting the admixtureof flux with the ore and fuel at the top of the stack, in shielding orguarding the ore and metal from silicious and other acids, inintroducing the oxidizing-blast at the zone of fusion, and inintroducing finely-comminuted basic flux at the zone of fusion at orabove said blast and into direct contact with the globules or smallbodies of molten metal while being smelted, substantially as described.

In testimony whereof I affix my signature in presence of two witnesses.

NATHANIEL A. PRATT.

\Vitnesses:

T. R. STUART, WM. SEOTUR.

